Introduction: typically spiny with densely granulate or tuberculate exoskeletons. This is a concept of the order that includes the Odontopleuridae and Damesellidae, more recently considered members of a related, but distinct order Odontopleurida. Examine an alternate handling of Order
Lichida that does not include the odontopleurids or damsellids.Cephalon: opisthoparian sutures; glabella broad, large, extending to anterior border, unusal lobation distinguishing a longitudinal lobe and lateral lobes; such lobation relatively simple (Dameselloidea & Odontopleuroidea) to complex with fused lateral and glabellar lobes (Lichoidea); eyes typically present, holochroal, usually not large; conterminant hypostome; typically with genal spines, sometimes greatly extended.Thorax: variable, 8-13 segments, usually spine-tipped, sometimes with distinctive spines (e.g., Odontopleuroidea).Pygidium: typically isopygous to macropygous, but sometimes short (e.g., Odontopleuroidea), otherwise often longer than wide, with 3 or more pairs of furrowed pleurae, typically ending in spinose tips. Other: similarities in protaspides of Lichidae and Odontopleuridae suggests common ancestry, but this relationship controversial (see Classification Notes below).Occurrence: Middle Cambrian to Devonian (Frasnian) Superfamilies: Lichoidea, Odontopleuroidea, Dameselloidea.

ADDITIONAL CLASSIFICATION NOTES FOR LICHIDA: Fortey (1997) lists Lichoidea, Odontopleuroidea, and Dameselloidea as constituent superfamilies of Order Lichida. Some treatments recognize an Order
Odontopleurida separate from Order Lichida, although protaspid similarities suggest the two are ultimately related; both lichid and odontopleurid protaspides possess distinctive paired spine or tubercle patterns on cephalon and protopygidium, have an anterior border, distinct axis, and marginal spines on protopygidium (Thomas & Holloway 1988). However, Whittington (1956) points out that the lichid protaspis is twice the size of those of odontopleurids. Odontopleurid protaspide hypostomes also lack slits on the lateral hypostomal border borne by those of lichids (and styginids). Despite both groups being ornamented with tubercles and typically spiny, the lobation of the glabella, complex in both, show some major differences in origin (lichid lobes arising from the axial furrow, while odontopleurid lobes arise via standard glabella development (Tripp & Evitt 1981). Whittington (2002) adds that the Odontopleuridae and Lichidae differ in several other respects, including ornamentation (primarily granules and tubercles in lichids, spines in odontopleurids), extent of ventral calcification (extended doublure with terrace ridges in lichids, not developed in odontopleurids), and hypostome size (larger in lichids). Even if both lichids and odontopleurids are kept in one order (Lichida), it is acknowledged that despite their common origin, they have diverged significantly in the course of their evolution. The primitive family Lichakephalidae includes genera that have affinities to Lichidae and others to Odontopleuridae, and some workers (e.g., Shergold et al 2000) do not accept the synonymy of Eoacidaspididae and Lichakephalidae. Examination of Cambrian lichakephalid/eoacidaspidid genera Acidaspides and Acidaspidella (Bruton
1983)
suggest they should be assigned to Odontopleuridae. This suggests that the Lichakephalidae as listed above is paraphyletic, and not all members should be included in Lichoidea. If Lichakephalidae is monophyletic, then it serves as the uniting taxon for an Order Lichida that includes both lichoids and odontopleuroids; if not, then some genera should be assigned to Odontopleuridae and others retained in Lichakephalidae. Fortey (1990) included the M-U Cambrian Damselloidea as a sister group to Odontopleuroidea, citing several characters: 1) narrow, ledglike anterior cranidial border, against which glabella abuts sharply, 2) deeply scribed, inflated eye ridges, 3) transverse hypostome with wide posterior border, 4) spinosity, especially on pygidium and anterolateral margins of free cheeks, 5) occipital tubercle without thoracic homologs 6) 3rd glabellar lobe reduced or absent. Presence of Acidaspides
praecurrens and 'odontopleurid protaspides' in Upper Cambrian Kazakhstan attributable to dameselloids further strengthen this relationship (Fortey pers com 2007). Primitive Ordovician lichakephalids (e.g., Lichakephalus) bear pygidia that are unlike typical lichids, some being arguably styginid-like, however Whittington (2002) suggests that a close relationship between lichids and styginids appears unlikely. If so, then sister taxon to the primitive Lichida might be found in the paraphyletic Redlichiida. In 2005, Pollit et al applied cladistic analysis to the Superfamily Lichoidea (Lichidae+Lichakephalidae) and proposed subfamilial and tribal subdivisions for the family Lichidae. Click here for a cladogram of Lichoid
relationships from the Pollit et al 2005 paper (warning, large graphic file). Expanded and complete genera listings for the families above adapted from Jell & Adrain (2003).